Power consumption is a very important issue for modern integrated circuits (ICs). Low power consumption is often a desired attribute of all types of electronic devices. However, power conservation can be especially important for portable devices that rely on battery power.
To improve power conservation, many integrated circuits can feature a low power mode (also referred to as a sleep mode). The low power mode can be such that an IC in this mode will consume minimal power while also having reduced functionality. The low power node can be utilized when the IC is not needed. For example, the microprocessor of a notebook computer may go into low power mode when a user closes the notebook without turning it off.
Most digital ICs can include one or more digital interfaces used for communications with the outside world. Operating the digital interfaces usually requires a significant amount of logic and power from the IC. For example, the digital interfaces can be synchronous, and operating them can require generating a clock signal. Therefore, many existing ICs can power down their digital interfaces during sleep mode. However, that means that these ICs cannot receive a signal to power up from the outside world through the digital interface. Thus, many existing ICs include dedicated analog interfaces for the purpose of receiving power-up and power-down signals. Analog signals can be easier to process, and processing them need not require much power.
However, the additional analog interfaces can add significant cost to an IC and the device it is connected to. For example, the analog interface can require additional pins for the IC, additional wires on a printed circuit board (PCB) on which the IC is positioned, additional pins on a second IC that controls the first IC's functionality, etc. These requirements may add up to a noticeable cost increase.
Another existing approach is not to place any low power circuitry into the IC, but to simply remove power coming into the IC. However, this approach can require another external circuit to disconnect power from the IC. Again, this can significantly increase the cost of a device because of additional components required and additional space requirements on the PCB.